The present invention relates to a hydraulic circuit for charging a hydraulic accumulator where the accumulator is used to power an additional function such as a hydraulic brake valve.
It is conventional to provide an accumulator charging valve which restricts pump flow thereby allowing a part of this flow to be used for the purpose of charging an accumulator when the accumulator pressure drops below a predetermined pressure level. When the accumulator is recharged to a preset level, the charging valve automatically halts the charging of the accumulator and permits unrestricted pump flow.
A disadvantage of known accumulator charging circuits is that the entire pump flow passes through the charging valve which results in the charging valve being relatively large, complex, and expensive. Thus, there has been a need for an improved accumulator charging circuit and charging valve arrangement which eliminates the need for conventional complex and expensive charging valves.
It is also common in earth-working equipment, such as backhoes, loaders and the like, to provide a fluid flow divider between the steering control valve and an auxiliary hydraulic circuit for operating the load handling mechanisms. The interest in steering systems having high pressure carryover capability has been increasing in recognition of the need to use available power sources more efficiently. A hydrostatic power steering system having a high pressure carryover capability makes it possible to operate both the steering motor and an auxiliary device such as a backhoe or loader bucket using only one pump, while converting a greater amount of the input energy to that pump into useful work.
Accordingly, it is an object of the present invention to provide a hydrostatic power steering circuit of the type which is capable of providing pressurized fluid to an auxiliary fluid circuit while giving priority to the demands of the steering circuit. It is a further object of the present invention to include within the hydrostatic power steering circuit an accumulator charging circuit and improved charging valve arrangement where the accumulator is charged to power an additional function such as a hydraulic brake valve.